Yarn package unwind performance is adversely impacted by formation of running bands which lead to fabric defects and yarn breaks. Higher levels of running bands lead to higher levels of fabric defects and yarn breaks. Moreover, running bands are aesthetically bad in that a customer would rate a running band free package as more desirable.
Running bands include masses of individual threadline reversals which have been dislodged inwardly from their winding position at the edge of the package due to the action of the unwind rollers. Keeping the reversals in their original position in the package is preferred to prevent an uncontrolled mass of dislodged reversals. The package edge, also referred to as the shoulder, tends to be higher than the center of the package due to the additional yarn deposited in the reversal as the traverse guide slows down, changes direction, and then speeds up again during winding of a yarn package.
During unwinding of a yarn package, the raised package shoulders allow unwinding rollers to focus their driving forces into this area tending to dislodge reversals. Furthermore, the raised package shoulders have a sloped profile which causes or promotes the additional dislodging of reversals.
One method for winding a yarn package is disclosed in U.S. Pat. No. 3,638,872, incorporated by reference herein, in its entirety. The method includes winding a hard yarn such as nylon onto a package, which reduces ribbon formation by periodically decreasing the rate of the peripheral package winding speed coincidently with and proportional to a periodic increase in traverse rate.